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    2. pdfWe measured the water flux across composite proton exchange membranes containing silica and SBA-15 fillers. The experiments were carried out using a gated cell in order to control the temperature and relative humidity (80 to 100 ºC, and 10, 50, 100%, respectively). The morphology was studied by scanning electron microscopy (SEM) and EDXS.
    3. pdfThe separate anodic and cathodic overpotentials in a proton exchange membrane fuel cell (activation, ohmic, concentration and mass transport) were measured in conventional and segmented hardware via reference electrodes, and multi-omponent gas analysis.
    4. pdfA composite membrane containing ZrO2 was tested under simulated and real fuel cell operations. To simulate the fuel cell environment, the composite membrane was tested on a gated cell at low relative humidity (10 %) and high temperature (100 °C). The water flux on the composite membrane was found to be higher than a commercial membrane (Nafion 115), suggesting that under these conditions water molecules are entrapped into the membrane matrix via dipole – dipole interactions.
    5. pdfA recently proposed vaporization exchange model for water sorption and flux in Nafion-type polymer electrolyte membranes is modified in order to treat transient water flux data.
    6. pdfWe introduce a signal-based diagnostic methodology that can isolate PEM fuel cell low anode and cathode flow rates. The methodology is based on calculating symptoms of the faults, and comparing them versus thresholds that are calibrated a priori of real time operation.
    7. pdfIn this work a 50-channel characterisation system for PEMFCs is presented. The system is capable of traditional electrochemical measurements (e.g. staircase voltammetry, chronoamperometry and cyclic voltammetry), and concurrent EIS measurements.
    8. pdfWe introduce a novel ex situ method of investigating the water transport in porous media for PEM fuel cells with an environmental scanning electron microscope (ESEM).
    9. pdfThe membrane permeabilities under concentration and pressure gradients are defined. The influence of the catalyst layer (CL) to water permeation is discussed by quantifying the water permeation fluxes of PEMs and CCMs of the same type. Vapour-dry permeation (VDP) and liquid-dry permeation (LDP) measurements showed the insignificant influence of the presence of the CL.
    10. pdfIn this work, pressure-induced voltage oscillations are explored as a novel diagnostic tool for PEFC cathodes. In this method, a small signal oscillation is imposed on the cathode outlet pressure. As a response to this pressure perturbation, the fuel cell
    11. pdfExperiments conducted on a commercial fuel cell humidifier indicate that the water recovery ratio is the best performance metric because it considers the water supplied to the humidifier. Data from a porous polymer membrane with a hydrophilic additive wer
    12. pdfWater transport across Nafion membranes was investigated under activity gradients at atmospheric pressure. The activity gradients across the membrane were controlled by exposing one side of the membrane to dry gas under laminar flow, while maintaining liquid or vapour equilibrium with water on the other side of the membrane.
    13. pdfElectrochemical Impedance Spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance.
    14. pdfWe present a non invasive method for the early diagnosis of flooding, dehydration and low fuel stoichiometry (three common failure modes). Our method is based on micro sensing electrodes (SE) that are placed at appropriate locations in a single cell. These electrodes have a characteristic potential response to each of the failure modes, which enables detection prior to overall fuel cell failure. The specific features in the measured responses (or combinations thereof) can be used to discern between different failure modes, and initiate corrective actions.
    15. pdfThis paper is a review of recent work done on accelerated stress tests in the study of PEM fuel cell durability, with a primary focus on the main components of the membrane electrode assembly (MEA). The accelerated stressors for each component under different conditions are outlined, in an attempt to gain a detailed understanding of cell degradation with respect to microstructural change and performance attenuation in the perfluorosulfonic acid membrane, catalyst, and gas diffusion layers.
    16. pdfThis paper discusses the latent effectiveness and the latent number of transfer units (NTU) for mass transfer in membrane humidity exchangers as proposed by L.Z. Zhang and J.L. Niu. We report on three limitations: 1. the use of a constant enthalpy of vaporization derived from the reference temperature in the Clausius-Clapeyron equation; 2. the use of an incorrect power on the Lewis number in the Chilton-Colburn analogy; 3. the simplification used in order to make a linear relationship between relative humidity and absolute humidity.
    17. pdfWe report on the separation of anodic and cathodic potentials in a working fuel cell via reference electrodes at constant conditions. The reference electrodes are not affected by the operating conditions of the fuel cell. Sensing electrodes placed at the fuel and oxidant inlet and outlet were used to provide localized information on the operating conditions and the state of the membrane electrode assembly (MEA).
    18. pdfDurability studies of the individual components of a PEM fuel cell are introduced, and various degradation mechanisms are examined. Following this analysis, the emphasis of this review shifts to applicable strategies for alleviating the degradation rate of each component. The lifetime of a PEM fuel cell as a function of operating conditions, component materials, and degradation mechanisms is then established.
    19. pdfA model is developed to describe sorption or desorption of water from Nafon slabs with one face contacting stagnant water or saturated water vapor and the opposite face exposed to flowing gas. Interfacial kinetics is considered along with bulk water transport. Simplifying assumptions yield several analytical formulas that relate the steady-state response to the gas flowrate. The results correlate well with data gathered under various experimental conditions. Two formulas applicable to transient measurements are also proposed.
    20. pdfA design methodology, involving a series of design equations, for plate and frame membrane humidifiers has been developed. Humidifiers of different flow channel geometries were created with a rapid prototyping technique.The ratio between the residence time of gas in the humidifier over the diffusion time of water from the surface of the membrane into the channel can be used as a design parameter. A target range between 2.0 and 4.0 was identified (with a nominal desired value of 3.0). A humidifier design procedure and suggestions are presented based on this parameter and the packaging requirements of the humidifier in a fuel cell system.
    21. pdfA simplified 2-dimensional axi-symmetric model for predicting the gas temperature and pressure rise in a hydrogen cylinder during the fill process is presented. The results are then compared with in-situ measurements of the average temperature rise inside a working compressed hydrogen cylinder during filling. The model is able to predict the average temperature rise within the cylinder to within 4K.
    22. pdfWe report on results obtained with single-phase vapour to vapour, counter flow operation. We found that moisture transfer is more strongly influenced by the flow rate through the receiver side than the donor side. We also measured the dew point profiles for both donor and receiver sides for various temperature conditions. No stream wise variation in moisture flux was observed, and the average flux value increased from 3.3x10-5 kg s-1m-2 at 30°C to 2.0x10-4 kg s-1m-2 at 70°C under fully humidified donor-side inlet conditions.
    23. pdfThis work discusses failure detection and isolation in proton exchange membrane fuel cells (PEMFCs). The collected spectra were modelled with an equivalent circuit whose time constants corresponded to ideal and Warburg components. Despite the qualitative limitations of this model, the measurements can discern between two failure modes.
    24. pdfWe measured the GDL compressive strain under steady-state and freezing conditions, and the effects of freezing conditions on GDL properties (electrical resistivity, bending stiffness, air permeability, surface contact angle, porosity and water vapor diffu
    25. pdfA type 3, 74 L hydrogen cylinder was instrumented internally with 63 thermocouples distributed along the mid vertical plane. The experimental fills were performed from initial pressures of 50, 75, 100, 150, and 200 bar at fill rates corresponding to nomin
    26. pdfTwo PEMFC failure modes (dehydration and flooding) were investigated using in-situ electrochemical impedance spectroscopy (EIS) on a four-cell stack under load. The EIS measurements were made at different temperatures (70 and 80oC).
    27. pdfThe energy consumption and greenhouse gas emissions of all private and transit vehicles from the Lower Fraser Valley in British Columbia, Canada were analysed for the year 2000. The energy figures were then compared with the Provincial renewable energy resources.
    28. pdfWe proposed a conceptual design for enhanced hydrogen production incorporating biological processes. The system under consideration involves the modification of existing schemes where biomass gasification is achieved through combustion and pyrolysis
    29. pdfWe described techniques and hardware for assembling non-planar membrane-electrode assemblies (MEAs) and the performance of two prototype cells based on the new designs. Preliminary results demonstrated significant gains in volumetric power density.
    30. pdfAn energy system design methodology was presented. It was based upon the perspective that energy system evolution is towards configurations which improve SERVICES, and is determined by barriers and attractors that can be technical, cultural, economic, or political.
    31. pdfWe modified a commercial two-stage GM cryogenic refrigerator to reduce its minimum, no-load temperature from 6.1 ± 0.1 K to 3.42 ± 0.05 K at a nominal operating frequency of 1.2 Hz. This was accomplished by using a monolithic regenerator.
    2. pdfThis invention is related to hybrid vehicles (fuel cell/electric) that can be refueled via water and electrical grids. The onboard refueling technology is based on capacitive de-ionisation (for water purification), solid-state electrolysers (for fuel production) and PEM fuel cells (for propulsion and hotel loads.
    3. pdfThis invention describes an improved oxidant flowfield based on internal turbulence-enhancing elements. The non-continuous channel cross sections are manufactured using conductive inks and screen-printing technology.
    4. pdfElectrochemical impedance spectroscopy is used as a diagnostic technique to detect and identify failures in operating proton exchange membrane fuel cells.
    5. In this invention, metallic flowfield plates and plastic components (gaskets, manifolds, etc) were used to assemble a PEMFC. The functional planes (oxidant, separator, fuel) were collapsed into a single plane.
    6. pdfThis invention describes a non planar fuel cell architecture that is consistent with unidirectional manufacturing processes. Specific challenges related to sealing, contact resistance, and corrosion are discussed.
    7. pdfA manufacturing technique for flexible membrane electrode assemblies (MEAs) is described.
    9. pdfA monolithic regenerator was fabricated using a cryogenic epoxy. The regenerator was then placed in a GM cryocooler to reduce the minimum temperature below 4 K.
    2. pdfNano-fibrous substrates of varying density were fabricated from polyacrylonitrile using electro-spinning techniques. The substrates were coated with cross-linked polyetherpolyurethane copolymers. The nano-fibrous membranes demonstrate a new type of membrane for selective water vapour transport.
    3. pdfA segmented cell was used to impose different current loads on isolated active area regiosn. The resulting differences in water generation rated were monitored by measuring the high frequency resistances in neighbouring segments.
    4. pdfSpatially resolved measurements on 49 independent segments in a working PEMFC have enabled the characterisation of humidification profiles under non-homofgeneous current density operation.
    5. pdfWe report on the sorption isotherms for commercial catalyst coated membranes (CCMs).
    6. pdfA four chamber cell was used to make dynamic temperature measurements on membrane electrode assemblies (inclding the diffusion media layers).
    7. pdfSegmented fuel cell hardware was used to illustrate the a multi-channel characterisation system. The results reported here include steady-state data for cell characterisation under galvanostatic and potentiostatic control as well as spatially resolved impedance spectra.
    8. pdfA fifty-channel characterisation system for PEM fuel cells is presented. The system is capable of traditional electrochemical measurements (e.g., staircase voltammetry, chronoamperometry and cyclic voltammetry), and concurrent EIS measurements.
    9. pdfTransient water transport experiments on Nafion of different thicknesses were carried out in the temperature range of 30 to 70 °C. These experiments report on water transport measurements under activity gradients in the time domain for liquid and vapour equilibrated Nafion membranes.
    10. pdfReference electrodes are used to elucidate the voltage loss mechanisms at both electrodes in a working fuel cell.
    11. pdfA thermodynamic model predicts the heat and water transfer across a membrane in a membrane humidifier. Experiments were conducted to obtain the necessary information to make the model complete, and also to validate its use over a range of temperatures and flow rates.
    12. pdfThe design of experiments method was applied to create empirical models to evaluate performance of membrane humidifiers. Experiments were run and the results analyzed to develop a combined metric for humidifier performance, provide information regarding effects, and compare geometries and membranes.
    13. pdfWater transport across Nafion membranes was investigated under activity gradients at atmospheric pressure. The activity gradients across the membrane were controlled by exposing one side of the membrane to dry gas under laminar flow, while maintaining liquid or vapour equilibrium with water on the other side of the membrane. The measurements were made under steady state conditions.
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  1. W. Mérida, “Cleaner Passage: Benefits of Low Emission Public Transit”, Chapter 3 in “PATH TO PURCHASE: Moving to Fuel Cell Bus Fleets.” A report prepared for BC Transit, September 15, 2005 [25-38].
  2. W. Mérida, “Operating Point Effects on Fuel Cell Design.” A Report Prepared for Angstrom Power Incorporated, December 1, 2003 [133 pages].
  3. J.M. Le Canut, W. Mérida and D.A. Harrington, “Research and Development of a Fuel Cell Diagnostic Product,” progress report to Greenlight Power Technologies (project 4569126) June 28, 2002 [50 pages].
  4. T. Niet, G. McLean, and W. Mérida, “Fuel Cell Operation using Oxygen Enhanced Oxidant Flow.“ Prepared for Questair Industries, March 1, 2000 [30 pages].
  5. W. Mérida, "Fuel Cell Bus Deployment: Emissions Reduction and other Benefits," A Report prepared for the Trade & Investments Office, Victoria, BC, Canada November 7, 1998 [14 pages].
  6. W. Mérida, "A Review of Current Fuel Cell Technologies," Internal Report, Institute for Integrated Energy Systems (IESVic), Victoria, Canada November 15, 1998 [43 pages].
  7. W. Mérida, "The 1998 Fuel Cell Seminar: Clean Energy for Today's World," A Summary of the 1998 Fuel Cell Seminar in Palm Springs, California. IESVic, Victoria, Canada March 1, 1998 [21 pages].
    2. pdfA simplified 2-dimensional axisymmetric model is developed for predicting the gas temperature and pressure rise in a hydrogen cylinder during the fill process. The model is then validated by comparison with in-situ measurements of the average temperature rise and temperature distribution inside a working compressed hydrogen cylinder during the process of filling. The model is able to predict the average temperature rise within the cylinder to within 4K. Both experimental and model results show a large conical temperature gradient extending out from the cylinder inlet.
    3. GDL durability under conditions of water phase transition during freezing was investigated ex-situ. GDL ex-situ measures of thickness, electrical conductivity, mechanical behavior, contact angle, porosity and pore-size distribution were found to be durable to water phase transition through 50 freeze-thaw cycles. Measures of air permeability revealed a potential failure mode under freezing conditions: material loss arising from a structurally weakened MPL. It was reasoned that liquid water phase transition during freeze-thaw aging weakened the MPL structure. Aged GDL was shown to be much less durable than un-aged GDL with regards to MPL material loss from air flow across the GDL.
    4. A method of using electrochemical impedance spectroscopy (EIS) as a diagnostic tool was used to investigate the effects of thermal cycling on proton exchange membrane fuel cells. The focus of this thesis was the constructions of new hardware required to accomplish this goal. Unlike previous work, this study used a parallel load bank to draw the periodic current necessary for impedance measurements.
    5. Two failure modes related to water management in Proton Exchange Membrane fuel cells (dehydration and flooding) were investigated using electrochemical impedance spectroscopy as a diagnosis tool. It was hypothesised that each failure mode corresponds to changes in the overall stack impedance that are observable in different frequency ranges. This hypothesis was corroborated experimentally.
    6. A commercial two-stage Gifford-McMahon cryogenic refrigerator has been successfully modified to reduce its minimum, no-load temperature from 6.1 ± 0.1 K to 3.42 ± 0.05 K at a nominal operating frequency of 1.2 Hz. The cooling power at 4.2 ± 0.1 K was measured to be 0.430 ± 0.001 W with zero load at the first stage. The superconducting magnets in the AMRL have been designed to operate at 4.5 K. The refrigeration power available at this temperature was measured to be 0.504 ± 0.001 W with a simultaneous second-stage load of 20.06 ± 0.01 W at 42.8 ± 0.5 K.